I had battery Troubles. I thought it may have been the batteries I purchased from PepBoys. The batteries would only last about 2 months. If I let my truck sit for 2 weeks without starting it, the batteries would completely die. I replace a total of 4 sets or 8 batteries in my 2000 F450. after the 4 set of batteries went bad I had the alternator tested. it was putting out only 11.5 volts. I replaced the alternator. i had the charging systen check at AutoZone with the device they use and it showed the voltage regulator failure. I took the alternator off and replaced it with a newer one and retested with the same results. now could there be something else going on here or just 2 bad alternators fresh from auto part store? Help me out here!